1. Field of the Invention
The present invention relates to a semiconductor manufacturing execution system and a semiconductor manufacturing method in a CIM (Computer Integrated Manufacturing) system.
2. Description of the Prior Art
A semiconductor manufacturing line includes a box in which a plurality of silicon wafers, referred to as a lot, are housed as a unit of distribution. A CIM system has the primary function of managing progress of flow of this box. Semiconductor manufacturing is achieved through hundreds of processing steps referred to as a process for producing a finished semiconductor product. This process can be an oxidation process, etching process, a lithography process, and the like. These processes are integrated so as to produce a semiconductor product.
Information regarding such a series of processes, their order, and processing conditions are referred to as process flow information. In accordance with this process flow information, the lot is moved through the manufacturing process. However, the process flow differs relative to each product. That is, the method of process integration and the processing conditions for each process normally differ relative to making different products.
Recently, various user needs have caused increased demand for semiconductor memory type products. This demand has resulted in a tendency toward small-quantity production of multiple semiconductor or memory types. For a DRAM type memory, for example, the lot of one or a few types of DRAMs flows on one production line. The production of so many different product types requires that each lot includes only a few wafers instead of the usual twenty-five. Thus, a plurality of lots, each having a small number of wafers are required to be mixed-loaded and to be flowed together. Furthermore, for a trial manufacture line or the like, twenty-five wafers are processed by dividing the conditions of a certain process or the process is done again. Thus, the flexibility of the process flow information for dividing the conditions and for adding another process is regarded as more important than providing for mass production.
In a conventional semiconductor manufacturing execution system, one process flow corresponds to one type (kind) of product. However, a plurality of lots are present each corresponding to the one type of product. For example, in a DRAM mass-production plant, as many as thousands of lots are sometimes present each of the one type.
The progress of these lots of one type are managed in accordance with one process flow information associated with the one type in the execution system.
FIG. 1 is a block diagram showing a relationship between a lot and the corresponding process flow in manufacturing the one conventional type of product. For example, one process flow information is defined corresponding to one type of product. The process flow information comprises a plurality of processes. The process flow is given a processing order relative to such processes and processing conditions (such as a recipe) for the processing steps in each such process. A plurality of lots are allocated to the process flow on the system. A memory, in which a location of a lot relative to a current process of the process flow can be described, is prepared for the lots on the system. Whenever the processing is completed relative to a process in the process flow, next process information is acquired from the process flow information for the next process to be performed.
In such a manner, the current progress of each lot in the process flow can be managed on the execution system.
Such a managing method of lots passing through one process flow corresponding to one type of product being made causes some problems. That is, even if only one of the lots shown in FIG. 1 is requested to change its processing condition, the conditions of all the lots are changed. In such a managing system, a complete management of all the lots is impossible. For example, assume that the one type of product being produced requires one hundred processes. At a process number 50, shown in the process flow for the tenth lot, for example, a faulty oxide film is produced. Therefore, the condition of the process number 50 is changed, and hence the process number 50 is changed into a process number 50a. Then, an error occurs. Namely, although the following lot must be processed in accordance with the process flow including the condition of process number 50, it is processed under the processing condition of the process flow having the modified process number 50a.
FIG. 2 is a model diagram illustrating the relationship between the process flow and the lot in the execution system of a certain type. The process flow includes the order of the processes, each process number, and process content information. The same processing is performed for each lot. Lots #1 and #2 shown in this drawing are managed relative to one process flow. The current location of processing relative to that process flow is such that the lots #1 and #2 are located in process 4 and process 3, respectively. Each lot can identify its own location, but cannot recognize its behavior.
Assume that a particular lot alone is erroneously changed. When a form or the like is statistically totalized, the totalization must be carried out in consideration of this particular lot.
In addition, when the processing in a certain lot does not succeed as to a particular process of the process flow and the processing is done again, the process cannot be added to this lot alone as is the case with the aforementioned condition. It is also impossible to define the allocation of a divided process flow or the like for each lot. That is, the managing method by one process flow corresponding to one type of product has difficulty in the setup of a different condition for each lot and the addition/elimination of a process.